An electrophotographic image forming apparatus (which hereafter may be referred to simply as “image forming apparatus”) forms an image through the following steps: First, an electrophotographic photosensitive member, as an image bearing member, which is generally in the form of a drum (photosensitive drum) is uniformly charged. Then, an electrostatic latent image (electrostatic image) is formed on the photosensitive drum by the selective exposure of the various points of the uniformly charged portion of the peripheral surface of the photosensitive drum. Then, the electrostatic latent image on the photosensitive drum is developed into a visible image (toner image) with the toner in the developer. Then, the toner image on the photosensitive drum is transferred onto recording medium such as a sheet of recording paper, a sheet of plastic, etc. Then, the toner image on the recording medium is fixed to the recording medium by the application of heat and pressure to the toner image.
The residual toner, that is, the toner remaining on the peripheral surface of the photosensitive drum after the transfer process, is removed from the photosensitive drum by a cleaning device, as a cleaning means, which is equipped with a cleaning member.
An image forming apparatus such as the one described above requires to be replenished with toner. It requires also the maintenance of its various processing means. In order to make it easier to replenish the image forming apparatus with toner, and also to maintain the processing means of the image forming apparatus, a process cartridge system, which integrally places a photosensitive drum, a charging means, a developing means, a cleaning means, etc., in a cartridge which is removably installable in the main assembly of an image forming apparatus, has been put into practical usage. A process cartridge system enables an ordinary user to maintain an electrophotographic image forming apparatus by himself or herself. Thus, it can drastically improve an electrophotographic image forming apparatus in operability. That is, a process cartridge system makes it possible to provide an image forming apparatus which is excellent in usability.
For example, a cleaning device, with which a process cartridge such as the one described above, is provided with seals for keeping sealed the gaps which are present between the cleaning member and the cleaning device frame which supports the cleaning member.
Japanese Laid-open Patent Application H08-211740 discloses a method that can prevent toner from leaking from a process cartridge, by injecting a liquid, which solidifies into elastomer, into the gaps in the joint portions of the sub-frames of a process cartridge, and the gaps between the cleaning member and the frames of the process cartridge. According to this application, the gaps which are present at the lengthwise ends of the cleaning member can be kept sealed with elastomer.
Japanese Laid-open Patent Application 2004-37638 discloses a structural arrangement for preventing toner from leaking out of a process cartridge, by the placement of seals formed of foamed elastic substance, in the gaps between the cleaning blade and the cleaning blade supporting frame, at the lengthwise ends of the cleaning member. According to this application, toner is prevented from leaking out of a process cartridge, by the placement of a member formed of foamed elastic substance, in the gaps which are present between the cleaning member and cleaning device frame, at their lengthwise ends. That is, this structural arrangement can keep sealed the gaps which extend between the cleaning member and cleaning device frame, in the widthwise direction of the cleaning member, with a sealing member formed of foamed elastic substance.
However, separately carrying out the process for coating various portions of a process cartridge with liquid elastomer, and the process for pasting the seal formed of foamed elastic substance to the various portions of a process cartridge, to keep sealed the aforementioned gaps which extend in the lengthwise or widthwise direction of the cleaning member, adds to the number of steps for manufacturing a process cartridge, which in turn leads to an increase in the cost of manufacturing a process cartridge.
Further, forming a seal by injecting (pouring) liquid elastomer into the aforementioned gaps makes it possible that minute gaps will occur between the cleaning member and seal, because of the nonuniformity in shape and measurement among the process cartridge components such as the cleaning member.